1. Field of the Invention
This invention relates to lighting systems and more specifically to lighting systems for automobiles.
2. Description of the Known Art
In the past, lighting systems, such as those found in automobiles, usually consisted of a plurality of incandescent or halogen bulbs, acting as light sources, located near the front or rear of the automobile. Usually, these light sources had a fixed function. For example, certain light sources might function to provide forward lighting, while other light sources might provide rearward lighting. Or more specifically, and in the case of rearward lighting, certain light sources may be used to meet a stop/tail function, while other light sources would be needed to meet a sidemarker function. As automobile designs became increasingly complex and new and different styling options were required, such as those with a thin and elongated aspect ratio, the number of light sources required to provide complex designs generally increased. As the number of light sources generally increased, a variety of problems arose.
For example, as the number of light sources increase, there is a greater chance that one or more of these light sources will fail and need to be replaced. This can be especially problematic when a majority of the light sources are operating properly but some are not operating properly and need to be replaced. As more and more light sources are used, the frequency of replacement increases. Further, as the number of light sources increases, manufacturing cost rises. In addition, styling options may be constrained or limited based on package area required to accommodate the multiple light sources.
With the advent of high power light emitting diodes (“LEDs”) coming into common usage, the light pipe offers a solution to use less light sources. For example, instead of using a single row array of low power LEDs to illuminate the area of a lamp function, one LED at one end of the light pipe may be used to illuminate the same size area. Additionally, the light pipe offers a greater variety of styling options, which is in high demand in the automotive industry. Light pipes are generally well known in the art and operate by transmitting light via total internal reflection. The light provided to the light pipe can be generated by as few as one light source, minimizing the need for numerous light sources, while offering a variety of styling options.
However, light pipes have their limitations. For example, light pipes only direct light in a single direction, based on the optical elements, i.e. prisms, facing in one direction. Moreover, although the light may have a certain amount of angular spread, the light generally is distributed around a single direction. While providing light in a single direction is useful to meet a single lamp function, multiple light sources coupled with additional light pipes may be needed if multiple functions, or multiple illuminated areas, are required.